1. Field of the Invention
The present invention relates to aerological condition measurement methods and apparatus. More particularly, the present invention relates to a method and apparatus for measuring wind conditions at two or more positions and altitudes within the approach and departure flight path of an airport runway.
2. Description of the Prior Art
Of the many meteorological and aerological factors affecting the operation of aircraft, one of the least recognized but frequently encountered circumstances is that of wind shear. This phenomenon is characterized by a gradient increase in wind velocity from ground level to approximately 2000 ft. elevation.
The most significant consequence of wind shear on aircraft is the effect on pilot judgment in the vulnerable takeoff and landing operational modes. When the condition is present, a descending aircraft must be strongly corrected as to either power application or glide slope to avoid stall as the craft enters increasingly lower velocity wind.
Another aerological circumstance affecting aircraft flight safety in the near proximity of the ground is that of small, slowly moving thermals. Thermals are vertical axis cylinders of rapidly rising air that may occur over any surface that is either reflective of sun rays or highly absorptive thereof. Many airport runways are such surfaces. As air is heated by ground radiation and convection, it rises to be replaced by cooler air. Consequently, a flow pattern develops whereby cool, surrounding air rushes radially inward to be heated at the ground base of the thermal. If the thermal is centered over the down wind end of an active runway, landing aircraft making a conventional final approach into the normally prevailing wind are suddenly caught in a strong tail wind very near the ground which drives the craft toward the ground.
Since wind shear and ground thermal phenomena are both low altitude conditions, a pilot must be particularly alert to unusual changes in his craft's airspeed and rate of descent in the last few seconds of his final approach to avoid premature and destructive contact with the ground when caught in one of the phenomena.
There are few visual or other objective indicators to reveal the presence of shear and thermal wind conditions. Even the existence of shear conditions has only recently been sufficiently recognized as to organize a definition thereof. The United States Federal Aviation Administration defines the phenomena as a change in wind speed and/or wind direction in a short distance resulting in a tearing or shearing effect. Efforts to monitor such conditions in the proximity of airports by mechanical means have been few, if any.
As previously understood, the monitoring of wind shear has been prohibited by the need to place heavy measuring equipment within the subject flow stream such as from towers as required by the disclosures of U.S. Pat. Nos. 3,616,692; 3,477,372; 3,246,514 and 2,619,527 or from airborne vehicles of sufficient carrying capacity to sustain an instrument package as taught by U.S. Pat. Nos. 3,229,517 and 1,913,512. The obvious consequence to such monitoring is that the measuring equipment would have to be placed in or near the zone of flight operations thereby creating an obstacle to navigation more hazardous than the aerological condition to be avoided.
Although ground based monitoring devices such as that disclosed by U.S. Pat. No. 3,182,499 are available for the stated purpose, the level of technological sophistication occasions a prohibitively high cost and are only applicable at locations physically remote from the actual aircraft glide path.
3. Purpose of the Invention
It is, therefore, an object of the present invention to teach a method and apparatus whereby wind velocity gradients and direction anomalies in the near proximity of airport runways may be safely and continously monitored.
Another object of the present invention is to provide airport controllers and pilots with a direct, telemetered instrument or radar indication of surface wind direction and intensity at glide slope altitudes along an airport runway approach and departure route.
Another object of the present invention is to provide a relatively inexpensive wind shear and direction anomaly indicating system whereby a pilot may be informed of relative gradients in wind conditions as he approaches a landing.
Another object of the present invention is to provide a wind condition measuring technique and apparatus that is safe for deployment in the near proximity of aircraft in flight.